JPH03501702A - High speed curtain coating method and equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] High speed curtain coating method and equipment The present invention relates generally to curtain coating methods, particularly for coatings such as photographic film and paper. the use of curtain coatings in the production of photographic materials. more specifically The present invention is capable of achieving a high degree of precision, which is essential in the field of photography. An improved curtain coating method and method specifically adapted for high speed manufacturing operations. The present invention relates to a device for use in the field.

Shuri Koyoshi Among the many known photographic material application methods are Meets the demanding requirements of the photographic industry regarding fabric speed and especially the ability to apply multiple layers simultaneously. There are two things I found. The first method, known as bead coating, Beguin, U.S. Pat. No. 2.681., issued June 15, 1954. No. 294 and Russell U.S. Patent issued September 4, 1956 No. 2.761.791. The latter patent specifically applies to the production of photographic materials. Multilayer coating, in which two or more layers of coating composition are simultaneously applied to a moving support at Regarding. A second method known as curtain coating is Grylar (Gr). No. 3,632,374, issued January 4, 1972; and Hughes, U.S. Pat. No. 3.50, issued April 28, 1970. 8.947. The latter patent is particularly free in the manufacture of photographic materials. Simultaneously applying two or more layers of coating composition to a moving support by means of a falling curtain The present invention relates to a multilayer curtain coating method.

The curtain coating method provides uniformity in both the width and length directions. It is necessary to apply a coating layer of precise thickness to a continuously moving support material. It has many advantages, especially in the production of photographic materials. curtain coating Many of the advantages achieved by the method are due to the close proximity of the moving support to the application point. The fact that a free-falling curtain can be formed by a sliding hopper without It is recognized that it can be obtained from The bead coating method is used for photographic materials. Manufacturing was too highly developed by the time curtain coatings appeared. Therefore, it continues to be commonly used. Bead coat for applying photographic materials Research on bead formation involves controlling two stabilizing forces that affect bead formation. specific application zones were found to be necessary in order to establish a highly stable method. is directed towards. By controlling and stabilizing bead formation, a wide range of coatings can be achieved. It became possible to use fabric speed, layer viscosity and layer thickness. The stabilizing power is the first Beguin, disclosed in U.S. Patent No. 2.681.294. is the differential pressure (suction) applied across the coating bead to the coating point, as shown in Second, Nadeau, U.S. Pat. No. 2.9, issued September 13, 1960. 52.559, applied just before the point of application. (electrostatic chargeclifferential) be. Thus, both differential pressure and electrostatic charge help keep the beads within the application zone. In useful bead coating methods, the forces acting on the web, e.g. , the force exerted by differential pressure or electrostatic charge helps stabilize the beads and is maintained in wet contact with the moving web.

However, beads are not formed in the curtain coating method. (The mechanism of application action is clearly different.

For example, in the curtain rolling method, the curtain falls freely and then sufficient momentum to strike the moving support and stabilize the application point. Apply force and ensure a uniform wetting line on the moving support. The amount of momentum required is a curtain obtained by appropriate selection of flow velocity and free fall height.

In bead coating, it is necessary to obtain a uniform electrostatic charge force at the point where the coating material is applied. The preferred method is to create a uniform level of bonded polar charges on the support. . The bond charges include equal and opposite electrostatic charges on the two sides of the support. coating The support must have extremely high resistance to keep the charge on the support until it reaches the cloth point. It is required that the dielectric material has resistance. Charged support grounded As it passes over the applicator roll, the side of the support near the applicator roll transfers an electric charge to the applicator roll. reflect onto the roll surface and thereby reduce the charge on the support that is in contact with the applicator roll surface. Effectively neutralizes and creates an equal amount of net charge on the surface of the support being coated. This allows the application between the support surface and the grounded hopper mouth to An electrostatic field is created at the point of application. A transfer with a net charge on the surface to be coated. When a moving support passes over a grounded applicator roll, the electrostatic field of the charge is The applied charge is effectively neutralized by the charge reflected onto the coating roll surface.

However, it is extremely difficult to obtain a uniform electrostatic field at the point where the material is applied, and All subsequent patent disclosures since the disclosure of U.S. Pat. No. 2,952.559 It concerns the combined effect of electric polarity and charge force. For example, U.S. Patent No. 3.2 No. 06.323 is attracting attention. Other patents include photos at fairly low application speeds. The use of polar charge assist for bead coating of materials has been described.

These include U.S. Pat. No. 3,470.417 and U.S. Pat. , 203 and U.S. Pat. No. 3,671,806. Additionally, other patents discloses a method for measuring and controlling electrostatic fields to obtain the required amount of uniform charge. There is. These include U.S. Patent No. 3,531.314; ．． 730.753, U.S. Patent No. 3.702.258, U.S. Patent No. 3,757 , 163 and U.S. Pat. No. 3,549,406.

As briefly discussed earlier, bead coatings and curtain coatings include The mechanism of application involved is completely different.

In addition to the differences in the forces used to stabilize the coating at the point of application, the coating composition Application parameters such as viscosity, flow rate per unit width of application and smoothness of the substrate surface The effects are usually quite different between bead coating method and curtain coating method. B No. 4,001,024 discloses the In order to increase coating speed without affecting coating uniformity, the bottom layer Reduce the viscosity (by dilution) and thereby increase the wet coverage age) must be increased. Also rough support surfaces, e.g. textile surfaces or Surfaces are even more difficult to coat at high speeds. these places In all cases, as the coating speed increases, the coating bead breaks or becomes unstable. There is a strong tendency to Entrainment of air bubbles may spread in the coating. mosquito The relationship between the bead coating method and the above-mentioned bead coating method is similar. An opposite relationship is recognized. When curtain coating failure occurs at high coating speed , they increase the viscosity of the coating composition or reduce the wet coverage of the bottom layer or This can often be avoided by applying a coarse support each time.

On the other hand, in the case of curtain coating at high speeds, the flow rate per width is increased. This often leads to problems with “clumping” of the coating on the support; Usually the curtain speed at the point of application on the support is greater than the speed of the support being coated. It happens at the right time. However, in the case of lumps, the support speed is It also occurs when the temperature is larger than the degree. In this way, curtain control at high application speeds is possible. The curtain failure is caused by too high a curtain momentum at the point of application. It seems like something that happens because of something.

Fundamentally different applications involved in bead coating and curtain coating methods Considering these directly conflicting requirements arising from the mechanism, the support surface curtain coating by imparting a high level of electrostatic polar charge to the surface. It is truly surprising that we were able to obtain such unexpected benefits. Low rate The use of Bell's electrostatic field is well known and for bead coating methods. Solved the problems that occurred in high-speed curtain coating of photographic materials. There is no recognition in the prior art that it may be useful to do so. What is that? On the contrary, such a force has no benefit as long as there is adequate curtain momentum. It was believed that he was deaf. Failures observed in curtain coating at high speeds are , because the curtain coating momentum is too large (too much), the application Applying an electrostatic force to the point of application would make the situation worse if anything. It was thought that it would happen.

Such a force is not generated when the curtain momentum is more than an appropriate amount, but when the curtain movement is There was a possibility that it would be useful at low coating speeds where the amount of movement is insufficient. Maybe.

The inventor does not wish to be bound by a theoretical explanation of how the invention functions. However, if the electrostatic polar charge is a strong enough adsorbent to produce an even and defect-free coating, It is believed that an attractive force is created between the falling curtain and the support.

For curtain coatings when web speeds are increased to extremely high levels. Coating defects that occur in Sufficient, Viscous Friction) "The Mecha Called Power" It is hypothesized that it arises from ism.

The effect of “insufficient viscous friction” forces is the formation of a large amount of entrained air bubbles between the coating and the substrate, and Droplets of the composition form upstream of the point of application and protrude from the application in an elongated band. It is characterized by the presence of an elongated band that occurs when it comes. “Insufficient viscous friction “The force hypothesis suggests that the viscosity of the coating solution is too low, the flow rate is too high, or that the support This is suggested by the fact that the body surface is too smooth and cannot be applied evenly. “Not enough The problems arising from viscous frictional forces are extremely high in curtain coatings. Fabric speed, for example, at a web speed of about 250 cm/sec or more only appears. It also serves a clearly different purpose, namely to stabilize the applied beads. It is known that electrostatic polar charges are used in bead coating. In contrast, according to the present invention, a given high level of electrostatic polar charge Curtain coatings are utilized to solve these problems. high level of static The electrical polarity charge is clearly in the region where the curtain hits the web, in the appropriate direction. action, thereby ensuring successful application by the mechanism of curtain coating. It contributes to a substantial suction power which substantially increases the speed at which it can be used. More ingredients Physically, with the appropriate level of electrostatic polarity charge, certain combinations of operating parameters can be parameters such as web smoothness, flow rate, coating composition viscosity and At the same time, we have successfully achieved the highest quality standards of photocoating technology. can be operated at extremely high coating speeds while meeting

As explained above, the high speed curtain coating method of the present invention typically is performed at web speeds starting at about 250 C11/sec or higher. Approximately 1 ．． 000cm/sec or more with appropriate level of electrostatic It can be effectively used with the help of gas polar charges.

Main shell summer next day 1 The object of the invention is to provide a curtain for coating moving objects at extremely high coating speeds. An object of the present invention is to provide a coating method and apparatus.

The above object of the present invention is to advance an object along a path through a coating zone to is comprised of multiple layers of liquid coating composition and includes a free-fall car extending across the path. The coating is applied in one or more layers by impinging a ten on the surface of the moving object within the coating zone. method for applying a liquid coating composition to an object, forming a coating thereon; This can be achieved by a device. The present invention provides a method for applying the coating material to the object. Applying an electrostatic polar charge on the surface in an amount sufficient to ensure uniformity of the application. directed towards doing.

The present invention further provides the method of advancing the object along a path through the coating zone to coat one or more layers. a free-falling curtain comprising a layer of liquid coating composition and extending across said path; consisting of one or more layers impinged onto the surface of the moving object within the application zone. A method and apparatus for applying a liquid coating composition to an object, forming a coating thereon. , the object moves forward at a speed of 400 Cm/sec, and applying an electrostatic polar charge on the surface of the object to which the coating material is applied; of said charge, measured in volts, at any point above, measured in cm/sec. the speed of the object so that the ratio to the speed is small (1:1) Accordingly, the present invention is directed to a method and apparatus for selecting the amount of charge.

The present invention provides a method for applying a single layer or multiple layers of a liquid photographic coating composition to forming a free-falling curtain extending across the web and then applying said curtain. impingement onto said web within a zone to form a single layer or multilayer coating. Particularly suitable for the manufacture of elements. This improved method extends the web by at least 400 cm/ sec on the surface of the web to which the coating material is applied. Applying an electrostatic polar charge, at any point on the surface, said charge measured in volts to said speed measured in mouth/sec is at least 1:1. selecting the amount of charge according to the speed of the web.

It is further an object of the invention that the means for forming a free-falling curtain comprises electrostatic electrodes on a support. It comprises multiple slide hoppers whose sexual charges are bond charges or polar charges. Yes, and a means for applying an electrostatic charge is used immediately before the application zone and is grounded. packing roll and small (including at least one grid-controlled ion generator) This is achieved by a curtain coating device consisting of:

ΣDish Ω Presenting Single Star Muri Figure 1 shows that a predetermined level of electrostatic polar charge is applied to the web surface and then 1 is a schematic diagram of an apparatus for curtain coating a surface with a liquid application composition.

Figure 2 shows the electrostatic charge in a typical curtain coating method for producing photographic materials. 2 is a graph relating polar charge level to coating speed.

Figure 3 shows the coating assembly in a typical curtain coating method for producing photographic materials. 1 is a graph relating composition flow rate and application speed;

Indigo The invention is described herein with particular reference to the application of photographic materials. this Since the field of coating involves highly precise operations, the present invention is particularly useful in this field. It is useful. However, the invention is limited to use in the application of photographic materials. It is desirable to achieve a very uniform application at very high speeds without any problems. It can be advantageously used in any curtain coating operation. Single layer and multilayer Both curtain coating methods benefit greatly from electrostatic polar charges. Ru.

The problem of curtain coating that the present invention solves is that it requires extremely high coating speeds. For example, a typical example is 250c! At web speeds above l/sec Miokoru. for a clearly different purpose, namely to stabilize the applied beads. Conventional techniques for electrostatic charges in bead coatings, including the use of electrostatic charges of In contrast to the use of The preferred embodiments of the present invention solve these problems in high-speed curtain coating. In the new implementation B, the electrostatic polar charge at the point of application is reduced to a high level of bonded charge or is obtained by using a polarized support and a grounded applicator roll. It will be done. This behavior of a given high level of electrostatic polar charge in the curtain coating For convenience, such use is herein used to indicate that it is directly operative to achieve effective application. Polar charge assist High levels of electrostatic polar charge are often referred to as the use of In the direction of The curtain coating mechanism contributes to the Substantially increases the speed at which successful applications can be made. More specifically, Using precise levels of electrostatic polar charge to control web fabric, flow rate, and coating composition viscosity. using specific combinations of operating parameters such as temperature and curtain height. On the other hand, it also successfully meets the highest quality standards in the technical field of photocoating. This makes it possible to operate at substantially higher coating speeds.

As indicated above, the high speed curtain coating method of the present invention typically Performed at web speeds above 250C11/sec. Approximately 1,000cm /sec or higher speeds with the help of an appropriate level of electrostatic polar charge. can be used effectively.

Any type of curtain coating equipment can be used with the present invention. Wear. Thus, for example, application equipment may be of the overflow weir type, pressure extrusion type, slurry type, etc. It may be a curtain coating hopper of the side type or slide extrusion type.

However, slide hoppers are particularly preferred, especially for photocoating operations. The equipment can be adapted to perform single layer applications or multiple layers simultaneously. For example, Research Disclosure (Research Disclosure), Section 17553, Volume 175 , November 1978, for performing a full-body application or contact (ab For performing utting or non-contact striped applications. can be adapted to

The method of the invention may be in the form of a liquid, e.g. a solution, dispersion or suspension. 0-pipe spray that can be used to apply any material or material mixture that can In many cases where light is applicable, the coating composition is an aqueous composition, but organic Other liquid vehicles, or inorganic, may also be utilized and are well within the scope of the present invention. Included in what you do. If more than one layer is applied, each layer may be the same or different. These coating compositions can be mixed with each other. They may be miscible or immiscible.

As mentioned above, the method of the present invention is useful in the photographic field for multilayer photographic elements, i.e. It is particularly useful for the production of elements consisting of a support coated with multiple overlapping layers of photographic coating compositions. The number of individual layers used may be as high as 10 or more; In the surgical field, the liquid application compositions used are usually aqueous compositions, but organic Sexual compositions can also be used. In the manufacture of photographic elements, the applied Each layer must be extremely thin, i.e. the wet coverage should be at most 0.015 cm, and is generally much lower than this value, even if it is as thin as about 0.0001 cm. stomach. In addition, the layers must be of very uniform thickness, and thickness uniformity must be The maximum variation in is typically ±2%, and in some cases as small as ±0.5%. Sai.

The method of the present invention is suitable for use with any liquid photographic coating composition and is suitable for use with any liquid photographic coating composition. can be used with photographic supports of the type described herein and attached hereto. Photographic technology within the scope of these terms as used in the claims. includes all coating compositions and supports as utilized in the field; is intended.

Useful photographic supports include film substrates, such as cellulose nitrate film. , cellulose acetate film, polyvinyl acetal film, polycarbonate Film, polystyrene film, polyethylene terephthalate film, etc. Examples include polyester film 5 paper; glass; cloth; metal, etc. α-olefin polymers such as polyethylene and polypropylene, or other polymers, For example, paper supports coated with cellulose organic acid esters and linear polyesters may also be used if desired.

The term "photographic" usually refers to radiation-sensitive materials, but in the manufacture of photographic elements it is used as a coating on a support. Not all layers applied are themselves radiosensitive. For example, undercoat layer , pelloid protective layer, filter layer 1, antihalation layer, etc. are often applied separately and/or in combination, and these particular layers are radiation sensitive. isn't it. The invention also relates to the application of such layers, and herein The term "photographic coating composition" as used refers to the composition from which such a layer is formed. intended to be inclusive. Furthermore, the present invention provides electrophotographic materials as well as invisible radiation. All sensitive materials, including those sensitive to visible radiation as well as those sensitive to visible radiation. Radioactive materials are included within its scope.

More specifically, the photographic layer applied by the method of the present invention may contain a photosensitive material such as Silver halides, zinc oxide, titanium dioxide, diazonium salts, photosensitive dyes, etc. and other components known in the art for use in photographic layers. Can be done.

Various types of surfactants can be used to improve the surface tension and application of photographic coating compositions according to the invention. It can be used to improve sex. Useful surfactants include saponin ; polyalkylene oxide, (e.g. polyethylene oxide) and glyco nonionic surfactants such as water-soluble adducts of alcohols and alkylphenols; Anionic interfaces such as rukyl ali-rboriether sulfates and sulfonates activators; and arylalkyl taurines, N-alkyl and N-acyl β-aryls; Amphoteric surfactants such as minopropionate; alkylammonium sulfones Examples include acid betaine.

Aqueous photographic coating compositions typically contain hydrophilic colloids. Useful hydrophilic colo Examples of idos include proteins such as gelatin, protein derivatives; cellulose derivatives; polysaccharides, e.g. starch; sugars, e.g. dextran; Synthetic polymers such as polyvinyl alcohol, polyacrylamide and polyvinylpyrrolidone; as well as those disclosed in U.S. Pat. No. 3,297,446. Other suitable hydrophilic colloids include. Mixtures of said colloids are also desired. May be used if appropriate.

In a preferred embodiment of the invention, the coating composition is a gelatin silver halide emulsion. It is. A wide variety of silver salts, such as silver bromide, silver iodide, silver chloride, or mixed halides Using an emulsion containing silver genide, for example silver chlorobromide, silver bromoiodide or silver chloroiodide can be done. Conventional additives, such as hardeners, antifoggants, stabilizers, and A coating agent, a plasticizer, a developer, etc. can be included in the emulsion. For color photography The emulsion may contain a color-forming coupler or a color-forming coupler. or an emulsion adapted to be developed in a solution containing other color-forming substances. It's okay.

In accordance with the present invention, a predetermined high level of electrostatic polar charge is impinged on the web surface. Devices that can be used for this purpose are described in U.S. Pat. No. 0.753 and Research Disclosure, Section 16974, 1978 May (Industrial Opportunities Ltd, published by Ho mewell, ) Iavant Haw+pshtrePO91EF, UK ), the disclosures of which are incorporated herein by reference.

Can be used for single layer or multilayer coating by curtain coating method The device is described in US Pat. No. 3,508,947 to Hughes and Greiller, U.S. Pat. No. 3,632,374, Their disclosures are incorporated herein by reference.

Curtain coating hoppers used in the practice of this invention typically include free-falling An end guide is provided to guide the curtain and define its width. useful end The edge guide method is as described in the Greiler and Hughes patent mentioned above. Use of web-based terminal guides and research disclosures 17553, Volume 175, November 1978. This includes the use of the "distal body guide" technique.

Under typical curtain coating conditions used in the manufacture of photographic materials, approximately 25 Because polar charge assist was used at coating speeds slower than 0 cm/sec. There's usually not much you can get. Because polar assist at such speed The use of This is because other means can be used to achieve uniformity.

In addition to the level of electrostatic polar charge, web speed, curtain height, and Viscosity, flow rate of each layer, surface tension, application point on the application roll and properties of the web material. There are many other factors that influence curtain coating methods, including . All of these factors interact with each other in extremely complex ways, and all can have a significant effect on high speed applications.

When referring to the application point here, we are referring to either positive or negative angles. Also mentioned, the angle causes the plane defined by the free-falling curtain to , offset from the center point of the applicator roll supporting the web. Too wide a distance from the center point This can lead to undesirable failures in the curtain coating process, and A pitfall will occur.

The method of the invention comprises a free-falling carton of liquid coating composition that impinges on the surface to be coated. A predetermined high level obtained from the action of the tensile agent is sufficiently effective to increase the uniformity of application. It involves the application of an electrostatic polar charge at the bell. Therefore, irregular static electricity web or other materials that may acquire charge patterns or low levels of static charge. This is clearly different from curtain coating an object. irregular and Such accumulation of static electricity and/or low levels of electrostatic charge can come from a variety of sources. For example, transporting a web support over a series of rollers may cause irregularities on the web surface. A regular electrostatic charge pattern can be generated. In addition, it also improves the applicability. If the web surface is corona-activated with a You will get a turn. However, such a charge pattern is not suitable for the present invention. Not effective in overcoming problems in curtain coatings to be solved by do not have. This is because in order to solve these problems, it is necessary to Equivalent in substantially all respects to what was known as the effective minimum level or higher levels - typically at least 400 volts. This is because it is necessary that a polar charge be present on the surface to be applied.

In a preferred embodiment of the invention, the web or other object to be coated is Only move forward through the application zone at a speed of 400 cm/sec or more. An electrostatic polar charge is a charge (voltage) on the surface to be coated at any point on the surface. (measured in cm/sec) versus speed (measured in cm/sec) It is applied at a level such that the ratio is at least 1:1.

Therefore, for example, when coating at a speed of 400 cm/sec, at least A charge level of 400 volts would be used, but other factors, e.g. For example, supports with surface textures where coating uniformity is particularly difficult to achieve. Can be well over 400 if necessary by using Will. In particularly preferred embodiments of the invention, the electrostatic polar charge level ( in Porto) is equal to or higher than the web speed (in cm/sec), 200 About the web speed plus Porto, i.e. 400cm/sec shall be a polar charge level of 600 volts or more.

In the method of the present invention, the upper limit of the level of polar charge available is Due to practical considerations involved in design and composition and photographic emulsions or other coating compositions. It is determined by the requirement that the level is not strong enough to have an adverse effect on the environment.

In a preferred embodiment of the invention, the web surface is substantially uniform over the entire surface of the web. Apply a polar charge of a certain level. In other embodiments, coating uniformity Some areas of the web surface have higher levels of polarization than others to promote It is advantageous to provide a load. Thus, for example, some curtain coating methods In this case, the web extends beyond the end of the applicator roll, i.e. If the web is modified so that it is wider than the width of the applicator roll and therefore overhangs the roll, Ru.

This reduces the tendency of the coating composition to stick to the coating roll, for example. It may also be done for the purpose of In these methods, on the web of the overhanging area Problems can occur when trying to achieve a uniform application. In particular, In overhang areas there should be no applicator roll providing electrical grounding behind the web. For obvious reasons, there is a higher polarity on the web in the overhang area than on the rest of the web surface. Electric charge is less effective. For this reason, areas overhanging the applicator roll A higher level of polar charge can be applied to the web than the rest of the web surface. In the method of the present invention, it is desirable to This can be achieved by providing a replenishment charging means that applies a replenishment polar charge only to the web. can be easily achieved. Thus, for example, if the web is after passing under a charging means for applying a sexual charge and receiving a coating composition Before applying a polar charge, apply a polar charge to only the area of the web that will overhang from the applicator roll. the second charging means. The charge applied in these areas is Must be of the same polarity applied over the entire web surface. For illustrative purposes, it is preferred that the voltage level be two to three times as large as the If a polar charge of 800 volts is applied to the entire web surface, the overhang area will be Advantageously, the replenishment polarity charge is between about 1600 and about 2400 volts.

An alternative technique for methods where the web overhangs the applicator roll is For the particular application speed and application conditions used, the entire web surface, including the Charged to a uniform polar charge level substantially higher than desired, thereby overhanging to ensure uniform application on the web in the area where it is applied, as well as on the rest of the web surface. The goal is to give the appropriate level of polar charge to the This of course applies to the rest of the web There will be a higher level of polar charge on the surface than the minimum level required. , but this is usually not a problem.

The increase in coating speed that can be achieved by using the method of the invention is significant. stomach. For example, significant levels of polar charge assist can be achieved while maintaining comparable coating quality. Double the application speed compared to the highest speed that can be used with is possible.

Referring to the drawings, FIG. 1 shows three layers of liquid application using a multi-slide hopper. 1 is a schematic illustration of a coating method of the present invention in which compositions are simultaneously coated onto a web support. 1st As shown, web 10 is unwound from supply roll 12 and then tensioned. around roll 14 and then over a grounded metal roll 16 where the appropriate subject to a uniform level of electrostatic polar charge. The device for generating electrostatic polar charges is the grid. It is a controlled ionizer type. The first such ionizer is a series of electrically conductive Element 20: Grid combined with e.g. tungsten ronds or wires Contains the element 1 day. The grid 18 is connected to the D C'ia source 22 and is electrically conductive. Element 20 is coupled to a DC power source 24. The second ionization device is a DC variable power supply 2 electrically conductive element 3 connected to grid 26 and DC variable power source 32 connected to 8; Contains 0.

The function of the first ionizer is to remove polar charge deviations on the surface of the incoming web. It is to be. A high voltage series power supply provides a 15,000 volt voltage to conductive element 20. I can do it. This high voltage ionizes the atmosphere and the charged ions are transported through the grid 18. It is accelerated towards the web 10. The web 10 is connected by a power supply voltage to the grid 18. charged to a uniform level determined by Once the web reaches the grid potential Then the ions are no longer accelerated between the grid and web surface and have uniform polarity. A charge level is present on the web surface. The second ionizer generates a uniform potential at a high level. Controlling this level will help increase the level. This feature uses a variable output power supply. achieved. This output voltage is connected to an electrostatic voltmeter 34 that measures the voltage on the web. electrically controlled using a feedback loop comprising: to the control circuit 36 This voltage is then compared with the reference voltage and the power supply output voltage is automatically stepped up or down. pressure is applied to maintain a constant voltage level on the web 10.

After the web 10 has reached the desired uniform level of electrostatic polarity charge, the web is guided Rolls 40, 42, 44, 46 and 4 are then grounded coating roll 5 0 and this applicator roll receives emulsion from a suitable source (not shown). and a multi-sliding curtain that generates a free-falling curtain 54 that impinges on the web. A coating hopper 52 is used to apply a liquid coating composition to the web, e.g. Apply a three-layer coating solution of photographic emulsion. After passing over the coating roll 50, the web 1 0 is directed into a drying chamber 56 where the emulsion layer is exposed to hot air or other gaseous medium. It is brought into contact with the body and dried, then passed around a guide roll for 5 days and then placed on a take-up roll 60. It is wound up.

Figure 2 shows a typical method for coating a gelatin silver halide photographic emulsion onto a web surface. - The application speed and static required for uniform application of the ten-coating method. It relates the level of electrical polarity charge. The curve shown in Figure 2 is Substitutions for fabric conditions (although different combinations of application conditions would result in curve shifts) It is a table: Curtain height -12,5C11 Curtain flow rate - 1.5 to 6 g/sec per Ω in curtain - Viscosity of coating composition - 60 centipoise Work surface - glossy polyethylene Application point - -15°.

Uniform coverage has been achieved in the left-hand region of the curve, but this is not the case in photo-manufacturing operations. Non-uniform coating occurs on the right side of the curve, which seems to be undesirable. In other words, The curve represents the dividing line between satisfactory and unsuccessful applications.

As shown in Figure 2, 1. About 250C! At coating speeds up to I/sec No polar charge assist is required to prevent failed applications. about 250 and about 40 In the region of coating speeds between 0 em/sec, the curve gradually increases with polar charge This indicates an increased need for cysts. However, typically 250 At speed levels between approximately 400 em/see and No polar charge assist is provided as other means may be used to do so. curve The slope of is decreasing as the coating speed is further increased. Specific application used Achieves uniform coating over a speed range of 400 to 800 cIIl/sec under certain conditions. To achieve this, we need to calculate the charge (measured in volts) versus the speed (measured in Ω/sec). It should be noted that the ratio must be at least 1:1. The preferred embodiment further includes an additional electrostatic charge on the order of 200 volts, e.g. For example, 600 volts or higher for a web speed of 400 cm/sec. Higher polar charge levels may be required.

Figure 3 shows the flow rate of the coating composition per unit width of the curtain versus the coating speed. Regarding degrees. A uniform application area is shown, but this area is where poor quality application has occurred. is surrounded by a verifiable area. The size and shape of the uniform application area is determined by the curtain. the height of the coating, the viscosity of the coating composition, the coating point, the nature of the web surface and the electrostatic polarity charge. It depends on the level of assist.

In the unstable curtain region, the curtain flow velocity per unit width forms a stable curtain. This is an area where it is too late to move forward. In this area, curtains have many It splits into strands, making it impossible to form a uniform coating. lump In the (pudding) region, the curtain speed at the point of application of the material is lower than the web speed. It represents a large state. As a result, the coating composition builds up behind the curtain, creating vertical stripes. arise.

For any combination of operating conditions, using electrostatic polar charge assist, e.g. In other words, by applying a sufficiently high level of electrostatic polar charge to the web surface, uniform It is a particularly important feature of the present invention that the application area can be substantially expanded. be. In this way, by using electrostatic polar charge assist, non-uniform coating can be achieved. The coating speed at which this phenomenon begins to occur can be widened. Due to this, Allows certain coating machines to run much faster without making any sacrifices in coating quality. It is possible to operate at higher speeds, thereby producing much more product.

The invention is further illustrated by the following examples.

By tL-bead cowing method No. 2,761 except that the hopper was set to apply seven layers at the same time. using a multi-slide bead coating hopper similar to that shown in No. 791. used. The application product is Ektacolor paper (Ekta) containing seven separate layers. ColorPapar). The wet coverage and viscosity of the 7 layers are shown in Table 1. do.

Man's knee table Blue sensitivity (bottom) 32 or 37 6.5 or 4.6 middle layer 5 115 Green sensitivity 50 Ultraviolet filter 763 Red sensitivity 1432 UV filter 763 Overcoat 793 The viscosity of the bottom layer was adjusted by diluting it with water to obtain sufficient coating properties. Adequate spreadability and Defined as a stable coating system free of mottling, cross lines, microbubbles and other coating defects . Apply this product at high speed (400 cm/sec or more) It was hoped that it would be tried. Table ■ Achieved as a function of bottom layer viscosity and polar charge voltage Indicates the maximum coating speed that can be applied. As shown in Table ■, matte (rough) surface support and a glossy (smooth) surface support were used.

■ Bead cowing method 6.5cps 4.6cps 6.5cps 4.6cps Mat 300cm /sec 350cm/sec 350cm/see 400 mouths/see Gloss 3 50aa/sec 400cm/sec 400cm/see ＊＊＊　＊　4 Polar charges are not required for coating at 00 cm/see.

For matte surface supports, as shown in Example 1(a) and I(b) Dilution of bottom layer from 6.5 to 4.6 centibore allows maximum application speed of 300 As a result, the speed increases from 350cm/sec to 350cm/sec. The increase was 350 to 400 cm/sec. Example 1 (c) and I (d) As shown, if a polar charge of 350 volts is applied to the support in front of the coating zone, For matte surface supports, the maximum coating speed is 50% for highly dilute bottom layers. cm/sec increased to a maximum of 400 cm/sec. using a matte surface Depending on the viscosity of the bottom layer, the maximum coating speed can be improved by approximately 14% to 17%. Ru. Beads to the extent that polar charges higher than 350 volts can be applied It was found that the coating speed was not improved.

For glossy supports, speeds faster than 400c11/sec are sufficient. No polar charge was necessary to achieve good coatability. Glossy surface supports are generally 0-car coating that can be applied at a speed approximately 50cm/sec faster than the matte surface. For type supports, diluting the bottom layer from 6.5 to 4.6 centipoise , the maximum coating speed increased by 50 cm/sec.

Compared to the known bead coating method, curtain coat is used for applying photographic materials. One advantage of using the dipping method is that the bottom layer does not need to be diluted any further than the other layers. It is well known that this is the case. High dilution bottom for bead coating In contrast to the need to use layers. On the upper side, 40% of the water is It is in the bottom layer. This requirement requires a speed that can dry the continuously coated web support. tends to be limited. The bottom layer in the bead coating method is usually 10 cells. Stable free fall of less than 100 cm, preferably 3 to 5 centipoise The outer layer of the lower curtain is typically 40 centipoise or higher. Apply a high viscosity coating composition. The advantages of fabrics are well known and described by Lughes, U.S. Pat. 508.947, continuous and uniformly delicate photographic coatings The water addition requirements on the dryer where the material must be dried can be significantly reduced. This is one advantage.

anus-curtain coating The hopper is set so that seven layers of the coating composition can be applied at the same time. A multiple sliding curtain cord similar to that shown in Figure 1 of No. 3,508.947. using a ting hopper. Viscosity and wetting of all layers except the bottom (blue-sensitive) layer The coverage was the same as shown in Table 1. bottom (blue sensitivity) ) layer with a coating composition having a wet coverage of 20 microns and a viscosity of 26 centiboaz and a removal allowance. I got it. Table 1 shows the coating speeds obtained using the matte support side and the glossy support side. to be displayed.

■ Curtain coating Bottom layer viscosity 26 centiboaz, wet coverage 20 micron mat 400 cm/se c * * * * Polar charge is not required for coating at 400cm/sec.

The matte surface curtain coating data recorded in Table ■ Compare with the data for the matte surface bead coating. For bead coating Therefore, the polarity is 350 volts to apply at a maximum speed of 400 cm/sec. It was necessary to use electric charges, but the curtain coating method uses polar charge assist. It was shown that such speeds could be achieved without using .

However, the application requirements for glossy supports have been found to be quite different. and therefore cannot be predicted based on conventional knowledge of bead coating methods. For example, table m shows that if polar charge assist is not used, 26 centimeters With the Ciboaz bottom layer, only 300 Cm/36 (of It shows that only the maximum application speed is achieved. bead coating Table 2 on the Glossy Surface shows that the 400C This shows that a maximum coating speed of +a/sec was achieved.

Shiny surface support when a 700 volt polar charge is applied to the coating surface in front of the coating point. The body was able to apply force at a speed of 500 em/sec. . This results in a glossy support surface compared to that obtained without polar charges. Therefore, the achievable curtain coating speed has increased by at least 67%. It becomes. Using progressively higher levels of polar charge, as shown in Figure 2, In some cases, higher speed coating is possible.

Comparing these examples, bead coating methods that require a highly dilute (low viscosity) bottom layer The coating speed of photographic material using is approximately 400cm/sec. It is shown that there is a limit.

Application of photographic materials using the curtain coating method allows for even faster application speeds. It turned out, unexpectedly, that Use curtain coating If a high concentration (high viscosity) bottom layer is applied, it will not be as smooth as a glossy support. Applying very high levels of polar charge to coat the web support can easily reduce the It was unexpected that coating speeds of cm/sec or higher would be obtained. However, it became clear.

Application speed Submission of translation of written amendment (Article 184-8 of the Patent Law) Δ Month 2, 1990 Yoshi, Commissioner of the Patent Office 1) Takeshi Moon 1 Display of patent application PCT/US 87103190 2 Name of the invention High speed curtain coating method and device 3 Patent applicant Address: United States, New York, 14650° Rotinister. state Street 343 Name Eastman Kodak Company 4 Agent Specification High-speed curtain coating method and equipment Main plate country of origin The present invention relates generally to curtain coating methods, particularly for coatings such as photographic film and paper. the use of curtain coatings in the production of photographic materials. more specifically The present invention is capable of achieving a high degree of precision, which is essential in the field of photography. An improved curtain coating method and method specifically adapted for high speed manufacturing operations. The present invention relates to a device for use in the field.

Hikarijiri ■ Bean amount Among the many known methods of applying materials are the uniformity of the coating, ultra-thin layers, and wide coating speeds. Meets the photographic industry's stringent requirements regarding speed and especially the ability to coat multiple layers simultaneously. There are two things.

The first method known as bead coating is Beguin , U.S. Patent No. 2.681.294, issued June 15, 1954, and Russell ( Russell) U.S. Patent No. 2.761.791 issued September 4, 1956 It is described in. The latter patent specification specifically deals with moving supports in the production of photographic materials. Two or more layers of the coating composition are applied simultaneously. Concerning multilayer coating. car A second method known as ten coating is Greiller , U.S. Pat. No. 3.632.374, issued January 4, 1972, and H. No. 3,508,947, issued April 28, 1970. Are listed. The latter patent specification specifically deals with free-fall cars in the production of photographic materials. Multilayer coating in which two or more layers of the coating composition are simultaneously applied to a moving support by means of a tensile press. A curtain coating method is disclosed.

The curtain coating method provides uniformity in both the width and length directions. It is necessary to apply a coating layer of precise thickness to a continuously moving support material. It has many advantages in the production of photographic materials. curtain coating method Many of the benefits achieved by moving supports are very close to the application point. Due to the fact that a free-falling curtain can be formed by a sliding hopper without It is recognized that it can be obtained. The bead coating method is used to manufacture photographic materials. By the time curtain coatings appeared in the construction industry, they had become too highly developed. Therefore, it continues to be commonly used.

Research on bead coating for applying photographic materials has led to bead formation. In order to establish an extremely stable method to control the two stabilizing forces that influence It is specifically aimed at the application zones found to be necessary. Bead formation can only be controlled. A wide range of coating speeds, layer viscosities and layer thicknesses can be used by stabilizing the became possible. Stabilizing forces were first disclosed in U.S. Pat. No. 2,681,294. With a differential pressure (suction) applied across the coating bead to the coating point, as shown in No. 2,952.559, issued September 13, 1960. As shown in the table, the electrostatic charge difference (electros) applied just before the application point tatic charge differential). The difference like this Bead cords where both pressure and electrostatic charge help hold the beads within the application zone. In the ting method, the force acting on the web, such as differential pressure or electrostatic charge, is The more force exerted helps stabilize the beads and moves the beads into the web and wetting them. Hold in contact. However, in the curtain coating method, beads is not formed, and the mechanism of application action is clearly different. For example, curtain In the coating method, the curtain falls freely and gains considerable momentum. to apply sufficient force to impact the moving support and stabilize the application point. Ensure a uniform wetting line on the support.

The required momentum is determined by appropriate selection of curtain flow rate and free fall height. can be obtained.

In bead coating, obtain uniform electrostatic charge force at the point where the coating material is applied. The preferred method for this is to create a uniform level of bonded polar charge on the support. Ru. The bond charges include equal and opposite electrostatic charges on the two sides of the support. application The support is extremely expensive to keep the charge on the support until it reaches the application point. A dielectric material with resistance is required. A charged support is grounded The side of the support near the coating roll transfers an electric charge as it passes over the coating roll. The electric current on the support that is reflected onto the surface of the coating tube and is therefore in contact with the surface of the coating tube. effectively neutralizes the load and places an equal amount of net charge on the surface of the substrate being coated. This creates a gap between the support surface and the grounded hopper mouth. An electrostatic field is created at the point of application of the coating. It also has a net charge on the surface to be coated. When a moving support passes over a grounded application port -J, the electrostatic field of the charge is is effectively neutralized by the charge reflected onto the coated roll surface.

However, it is extremely difficult to obtain a uniform electrostatic field at the point where the material is applied, and All subsequent patent disclosures since the disclosure of U.S. Pat. No. 2,952,559 have It concerns the combined effect of electric polarity and charge force. For example, U.S. Pat. No. 06.323 is attracting attention. Other patents include photos at fairly low application speeds. The use of polar charge assist for bead coating of materials has been described. . These include U.S. Pat. No. 3,470.417 and U.S. Pat. No. 0.203 and U.S. Patent No. 3.671,806. In addition, other features discloses a method for measuring and controlling electrostatic fields to obtain the required amount of uniform charge. ing. These include U.S. Patent No. 3,531.314; 3,730.753, U.S. Patent No. 3,702.258, U.S. Patent No. 3,75 No. 7.163 and U.S. Pat. No. 3.549.406.

As briefly discussed earlier, bead coatings and curtain coatings include The mechanism of application involved is completely different.

In addition to the differences in the forces used to stabilize the coating at the point of application, the coating composition Application parameters such as viscosity, flow rate per unit width of application and smoothness of the substrate surface The effect of bead coating method is usually higher than that of curtain coating method. Totally different. For bead coating, see U.S. Patent No. 4.001,024. To increase coating speed without affecting coating uniformity, as disclosed In addition, the viscosity of the bottom layer is reduced (by dilution), thereby increasing the wet coverage (wet coverage). coverage) must be increased. Also rough support surfaces, e.g. Textile surfaces or pine I surfaces are even more difficult to coat at high speeds.

In all these cases, as the application speed increases, the application beads break or It has a strong tendency to become unstable, resulting in vertical and horizontal lines in the coated material or Entrainment of air bubbles into the coating at the border of the object. ) may spread. For the curtain coating method, please refer to the bead coating method above. A relationship that is exactly the opposite of that of ing is observed. Curtains with high application speed If coating failures are likely to occur, they may increase the viscosity of the coating composition or This can be avoided by lowering the wet coverage or applying a coarse support. On the other hand, in the case of high-speed curtain coating, the per-width Increasing the flow rate of the coating may lead to the problem of "clumping" of the coating on the support. This is usually due to the curtain speed at the coating point on the support being coated. This occurs when the speed is greater than the body's speed. However, the mass is It also occurs when the velocity is greater than the curtain velocity. Thus, high application speed Curtain coating failures are caused by the momentum of the curtain at the point of application. This seems to be caused by the price being too high.

The fundamentally different coatings involved in bead coating and curtain coating methods Given these very different requirements arising from the fabric mechanism, high in curtain coatings by imparting a level of electrostatic polar charge. It is truly amazing that we were able to obtain such unexpected benefits. low level The use of electrostatic fields is well known and developed for bead coating methods. However, it is difficult to solve the problems encountered in high-speed curtain coating of photographic materials. There is no recognition in the prior art that this may be useful. on the contrary , such a force would have no benefit as long as there was a suitable curtain momentum. It was believed. Failures seen in curtain coating at high speeds This happens because there is too much ten-coating momentum, so do not apply the coating material. I think that applying an electrostatic force to a point would make the situation worse if anything. I was worried. Such a force is not generated when the curtain momentum is more than a moderate amount. , which may be useful at low coating speeds where curtain momentum is insufficient. It might have been possible.

The inventor does not wish to be bound by a theoretical explanation of how the invention functions. However, if the electrostatic polar charge is a strong enough adsorbent to produce an even and defect-free coating, It is believed that an attractive force is created between the falling curtain and the support.

For curtain coatings when web speeds are increased to extremely high levels. Coating defects that occur in The mechanism called force It is assumed that it arises from the rhythm.

The effect of “insufficient viscous friction” forces is the formation of a large amount of entrained air bubbles between the coating and the substrate, and Droplets of the composition form upstream of the point of application and protrude from the application in an elongated band. It is characterized by the presence of an elongated band that occurs when it comes. “Insufficient viscous friction “The force hypothesis suggests that the viscosity of the coating solution is too low, the flow rate is too high, or that the support This is suggested by the fact that the body surface is too smooth and cannot be applied evenly. “Not enough The problems arising from viscous frictional forces are extremely high in curtain coatings. Only at fabric speeds, e.g., web speeds of about 250 cm/sec or higher. appear. A bead with a clearly different purpose, namely stabilizing the applied beads. What is known about the use of electrostatic polar charges in laser coating? In contrast, according to the present invention, a given high level of electrostatic polar charge is Ten coating is utilized to solve these problems. high level of static electricity Polar charges obviously act in the area where the curtain hits the web, in the appropriate direction. and thereby ensure successful application by the curtain coating mechanism. This contributes to a substantial suction force that substantially increases the speed at which the product can be used. more specific With the appropriate level of electrostatic polarity charge, certain combinations of operating parameters can be such as web smoothness, flow rate, coating composition viscosity and curtain while still successfully meeting the extremely high quality standards of photocoating technology. It is possible to operate at extremely high coating speeds while maintaining

As explained above, the high speed curtain coating method of the present invention typically is carried out at web speeds starting at about 250 cm/sec or higher. Approximately 1, 000Ω/sec or higher speed with appropriate level of electrostatic polarity It can be effectively used with the help of electric charge.

Main plate one after another The object of the invention is to provide a curtain for coating moving objects at extremely high coating speeds. An object of the present invention is to provide a coating method and apparatus.

The above object of the invention is to move an object along a path through a coating zone for at least 250 cm. m/see and consists of one or more layers of liquid coating composition. a free-falling curtain extending across said path of moving objects within said application zone; an object that is impinged onto a surface to form a coating consisting of one or more layers thereon; 0 that can be achieved by the method and apparatus for applying liquid coating compositions The invention provides a method for applying the coating material on the surface of the object to which the coating material is applied, at any point on the surface. , of said charge measured in volts, for said speed measured in cm/sec. of the charge according to the speed of the object such that the ratio of the charges is at least 1:1. It is directed to applying a selective amount of electrostatic polar charge.

Advantageously, the voltage is 200 volts greater than the voltage reached by said ratio.

The object to be coated is a web, and a single layer or multiple layers of the liquid photographic coating composition are applied to the web. forming a free-falling curtain extending across the web advanced along the path; Impingement of the curtain onto the web in a coating zone to produce a single layer or multilayer coating. Advantageously, embodiments of the invention are specifically intended for the manufacture of photographic elements, forming You get points. In a preferred embodiment, the web is at least 400 cm/s Move forward at ec speed.

1-cho” 11-E plate Figure 1 shows that a predetermined level of electrostatic polar charge is applied to the web surface and then 1 is a schematic diagram of an apparatus for curtain coating a surface with a liquid application composition.

Figure 2 shows the electrostatic charge in a typical curtain coating method for producing photographic materials. 2 is a graph relating polar charge level to coating speed.

Figure 3 shows the coating assembly in a typical curtain coating method for producing photographic materials. 1 is a graph relating composition flow rate and application speed;

Desirable amount of F The invention is described herein with particular reference to the application of photographic materials. this Since the field of coating involves highly precise operations, the present invention is particularly useful in this field. It is useful. However, the invention is limited to use in the application of photographic materials. It is desirable to achieve a very uniform application at very high speeds without any problems. (Can be advantageously used in curtain coating operations. Single layer and multilayer Both layer curtain coating methods benefit greatly from electrostatic polar charges. There is.

The problem of curtain coating that the present invention solves is that it requires extremely high coating speeds. For example, typically only at web speeds above 250 cm/sec. It happens. for a clearly different purpose, namely to stabilize the applied beads. Conventional techniques for electrostatic charging in bead coating, including the use of electrostatic charges. In contrast to the use of to solve these problems in high-speed curtain coating. static at the application point Electrical polar charges can be grounded with a support that has a high level of combined charge or polar charge. may be obtained by using a coated roll. curtain coating Such use of a predetermined high level of electrostatic polar charge in For convenience, it is used in the sense that it can be used directly to achieve effective application. This is called the use of “polar charge assist.” High levels of electrostatic polar charge, which often occur when the curtain is oriented properly, clearly contributes to the substantial attractive force acting in the area of impact, thereby , the coating can be applied successfully by the mechanism of curtain coating. Substantially increases the speed that can be achieved. More specifically, the appropriate level of electrostatic polarity Charge is used to control web fabric, flow rate, coating composition viscosity, and curtain height. using a specific combination of operating parameters such as It has successfully met even the highest quality standards in the field of textile technology, resulting in substantially higher It is possible to operate at high coating speeds.

As indicated above, the high speed curtain coating method of the present invention typically It is carried out at web speeds above 250 cm/sec. Approximately 1 + 000 cm/sec or higher speeds requires an appropriate level of electrostatic polarity. It can be used effectively with the help of cargo.

Any type of curtain coating equipment may be used to practice the present invention Can be done. Thus, for example, the applicator may be of the overflow weir type, the pressure extrusion type, or A slide type or slide extrusion type curtain coating hopper. good. However, slide hoppers are particularly preferred, especially for photocoating operations. . The coating equipment can be adapted to carry out single layer coatings or multi-layer coatings. It may be of the type that is applied at the same time. For example, research disk Research Disclosure, Section 17553, Section 17553. 175, November 1978. abutting or non-abbutting striped application can be adapted for implementation.

The method of the invention may be in the form of a liquid, e.g. a solution, dispersion or suspension. It can be used to apply any material or material mixture that can be used. Main departure In many cases where light is applicable, the coating composition is an aqueous composition, but organic Other liquid vehicles, or inorganic, can also be utilized. Multiple layers are applied each layer may be of the same or different liquid coating composition. and these coating compositions may be miscible or immiscible with each other. good.

As mentioned above, the method of the present invention is useful in the photographic field for multilayer photographic elements, i.e. It is particularly useful for the production of elements consisting of a support coated with multiple overlapping layers of photographic coating compositions. It is for use. The number of individual layers may be as high as ten or more. Photographic technique In the surgical field, the liquid application compositions used are usually aqueous compositions, but organic Sexual compositions can also be used. In the manufacture of photographic elements, the applied Each layer must be very thin, i.e. wet coverage up to about 0.015 -, -m is much lower than this value, about 0.0001 cm is very thin (but may be , in addition, the layers must be of very uniform thickness, and the thickness uniformity must be The maximum variation in stomach.

The method of the present invention is suitable for use with any liquid photographic coating composition and is suitable for use with any liquid photographic coating composition. can be used with photographic supports of the type described herein and attached hereto. Photographic technology within the scope of these terms as used in the claims. includes all coating compositions and supports as utilized in the field; is intended.

Useful photographic supports include film substrates, such as cellulose nitrate film. , cellulose acetate film, polyvinyl acetal film, polycarbonate Film, polystyrene film, polyethylene terephthalate film and others Examples include polyester film; glass; cloth; metal, etc. α-olefin polymers such as polyethylene and polypropylene, or other polymers, For example, paper supports coated with cellulose organic acid esters and linear polyesters may also be used if desired.

The term "photographic" usually refers to radiation-sensitive materials, but in the manufacture of photographic elements it is used as a coating on a support. Not all layers applied are themselves radiosensitive. For example, undercoat layer , veloid (pelloicl) protective layer, filter layer, antihalation layer, etc. are often applied separately and/or in combination, and these particular layers are radiation sensitive. isn't it. The invention also relates to the application of such radiation-insensitive layers; As used in the specification, the term "photographic coating composition" refers to the composition from which such layers are formed. is intended to encompass compositions that include. Furthermore, the present invention provides electrophotographic materials as well as All materials, including materials sensitive to invisible radiation as well as those sensitive to visible radiation, It is intended to include within its scope all radiation-sensitive materials.

More specifically, the photographic layer applied by the method of the present invention comprises a light-sensitive material, e.g. Silver halides, zinc oxide, titanium dioxide, diazonium salts, photosensitive dyes, etc. and other components known in the art for use in photographic layers. Can be done.

Various types of surfactants are used to improve the surface tension and coating properties of photographic coating compositions. Tamesha can be used. Useful surfactants include saponins; polyalkylene Ren oxide, (e.g. polyethylene oxide) and glycol and alkyl Nonionic surfactants such as water-soluble adducts of phenol; alkylarides anionic surfactants such as polyether sulfates and sulfonates; and Aryl alkyl taurine, N-alkyl and N-acyl β-aminopropione amphoteric surfactants such as alkylammonium sulfonate betaine; can be lost.

Aqueous photographic coating compositions typically contain hydrophilic colloids. Useful hydrophilic colo Examples of idos include proteins such as gelatin, protein derivatives; cellulose derivatives; polysaccharides, e.g. starch; sugars, e.g. dextran; Synthetic polymers such as polyvinyl alcohol, polyacrylamide and polyvinylpyrrolidone; as well as those disclosed in U.S. Pat. No. 3,297,446. Other suitable hydrophilic colloids include. Mixtures of said colloids are also desired. May be used if appropriate.

The coating composition may be a gelatin silver halide emulsion.

A wide variety of silver salts, such as silver bromide, silver iodide, silver chloride, or mixed silver halides For example, it is possible to use an emulsion containing silver chlorobromide, silver bromoiodide or silver chloroiodide. can. Commonly used additives, such as curing agents, antifoggants, stabilizers, matting agents, Plasticizers, developers, etc. can be included in the emulsion. For use in color photography The emulsion may contain a color-forming coupler or a color-forming coupler or May be an emulsion adapted to be developed in a solution containing other color-forming substances .

In accordance with the present invention, a predetermined high level of electrostatic polar charge is impinged on the web surface. Devices that can be used for this purpose are described in U.S. Pat. No. 0.753 and Research Disclosure, Section 16974, 1978 May (Industrial Opportunities Ltd, published by Ho mewell, Havant Hampshire PO91EF, UK) have been described, the disclosures of which are incorporated herein by reference. car Equipment that can be used for single-layer or multi-layer coating using the ten-coating method No. 3,508,947 to Hughes and U.S. Pat. (Greiller) U.S. Pat. No. 3.632.374, which The disclosures of which are incorporated herein by reference.

Curtain coating hoppers used in the practice of this invention typically include free-falling An end guide is provided to guide the curtain and define its width. useful end The edge guide method is as described in the Greiler and Hughes patent mentioned above. Use of web-based terminal guides and research disclosures 17553, Volume 175, November 1978. This includes the use of the "distal body guide" technique.

Under typical curtain coating conditions used in the manufacture of photographic materials, approximately 25 Application speeds slower than 0 Ω/sec benefit from using polar charge assist. There is usually not much that can be done. Because polar assist at such speed Their use usually does not materially affect the uniformity of the coating and does not result in satisfactory coating uniformity. This is because other means can be used to achieve unity.

In addition to the level of electrostatic polar charge, web speed, curtain height, and Viscosity, flow rate of each layer, surface tension, application point on the application roll and properties of the web material. There are many other factors that influence curtain coating methods, including . All of these factors interact with each other in extremely complex ways, and all can have a significant effect on high speed applications.

When referring to the application point here, we are referring to either positive or negative angles. The angle also affects the contact between the axis of the coating roll and the free-falling curtain. The plane defined by the contact line is the plane containing the axis of the coating roll and the coating supporting the web. Offset from the axis along the top of the fabric roll.゛If you move too far away from the center point, the Undesirable failures of the -ten coating process can also occur, resulting in coating defects. That will happen.

The method of the invention comprises a free-falling carton of liquid coating composition that impinges on the surface to be coated. A predetermined high level obtained from the action of the tensile agent is sufficiently effective to increase the uniformity of application. It involves the application of an electrostatic polar charge at the bell. Therefore, irregular static electricity web or other materials that may acquire charge patterns or low levels of static charge. This is clearly different from curtain coating an object. irregular and Such accumulation of static electricity and/or low levels of electrostatic charge can come from a variety of sources. For example, transporting a web support over a series of rollers may cause irregularities on the web surface. A regular electrostatic charge pattern can be generated. In addition, it also improves the applicability. If the web surface is corona-activated with a You will get a turn. However, such a charge nog turn is is effective in overcoming the problems in curtain coatings solved by There isn't. Because to solve these problems, it is necessary to apply static This is because it is necessary that electric polar charges exist. Preferably polar charges are At substantially all points on the substrate surface to be covered, the effective minimum level at a level equal to or higher than that previously known - typically at least 400 vol. This is the root level.

In a preferred embodiment of the invention, the web or other object to be coated is Only move forward through the application zone at a speed of 400 cm/sec or more. An electrostatic polar charge is a charge (voltage) on the surface to be coated at any point on the surface. (measured in cm/sec) versus speed (measured in cm/sec) It is applied at a level such that the ratio is at least 1:1.

Therefore, for example, when coating at a speed of 400 cm/sec, at least A charge level of 400 volts would be used, but other factors, e.g. For example, supports with surface textures where coating uniformity is particularly difficult to achieve. Can be well over 400 if necessary by using Will. In particularly preferred embodiments of the invention, the electrostatic polar charge level ( (in bolts) is equal to or higher than the web speed (in Cm/sec), 200 For web speed plus bolts, i.e. 400cm/sec shall be a polar charge level of 600 volts or more.

In the method of the present invention, the upper limit of the level of polar charge available is Due to practical considerations involved in design and composition and photographic emulsions or other coating compositions. It is determined by the requirement that the level is not strong enough to have a negative effect on the body.

In a preferred embodiment of the invention, the web is substantially uniform across the entire surface of the web. Apply a level of polar charge. In other embodiments, for coating uniformity purposes. A higher level of polar charge in some areas of the web surface than in other areas to promote It is advantageous to give Thus, for example, certain curtain coating methods In some cases, the web extends beyond the end of the applicator roll, i.e., the web It is modified so that it is wider than the width of the fabric roll and therefore overhangs the roll. this This can be done, for example, to reduce the tendency of the coating composition to stick to the coating roll. It may also be done on a regular basis. In these methods, a uniform Problems can occur when attempting to apply uniform coatings. Especially in overhang areas. The obvious reason is that there is no applicator roll behind the web to provide an electrical ground. The polar charge has a greater effect on the web in the overhanging area than on the rest of the web surface. low. For this reason, the web in the area overhanging the applicator roll is It is desirable to apply a higher level of polar charge than the surface of the web. Book In the method of the invention, only the area of the web that overhangs the applicator roll is refilled. This can easily be achieved by providing supplementary charging means to apply a polar charge. I can do it. Thus, for example, because a web carries a polar charge over its entire surface, the coating roll after passing under the charging means and before receiving the coating composition. a second charging means for applying a polar charge only to the area of the web that will overhang from the pass below. The charge applied in these areas spreads over the entire web surface. It must be of the same polarity as the one applied across it and 2 to 3 times as large. Preferably, the voltage level is approximately For illustrative purposes, the entire web surface If a polar charge of 800 pol I is applied, an additional polar charge is applied to the overhang area. Advantageously, the load is between about 1600 and about 2400 volts.

An alternative technique for methods where the web overhangs the applicator roll is For the particular application speed and application conditions used, the entire web surface, including the Charged to a uniform polarity charge level that is substantially higher than what would be required if there were no overhangs and thereby uniformly coat the web in the overhang area as well as the rest of the web surface. The goal is to provide the appropriate level of polar charge to ensure reliable application. this child This means, of course, that the remaining web surface has a higher level of polarity than the minimum level required. This means that there will be a charge, but this is usually not a problem.

The increase in coating speed that can be achieved by using the method of the invention is significant. stomach. For example, significant levels of polar charge assist can be achieved while maintaining comparable coating quality. Double the application speed compared to the highest speed that can be used with is possible.

Referring to the drawings, FIG. 1 shows three layers of liquid application using a multi-slide hopper. 1 is a schematic illustration of a coating method of the present invention in which compositions are simultaneously coated onto a web support. 1st As shown, web 10 is unwound from supply roll 12 and then tensioned. around roll 14 and then over a grounded metal roll 16 where the appropriate subject to a uniform level of electrostatic polar charge. The device for generating electrostatic polar charges is the grid. It is a controlled ionizer type. The first such ionizer is a series of electrically conductive Element 20: Grid combined with e.g. tungsten wood or wire comprising element 18. The grid 18 is coupled to a DC power source 22 while the conductive element 2 0 is connected to the DC power supply 24. The second ionization device is connected to a DC variable power source 28. a conductive element 30 coupled to a grid 26 and a DC variable power source 32; That's what happens.

The function of the first ionizer is to remove polar charge deviations on the surface of the incoming web. It is to be. A high voltage series power supply provides a 15,000 volt voltage to conductive element 20. I can do it. This high voltage ionizes the atmosphere and the charged ions are transported through the grid 18. It is accelerated towards the web 10. The web 10 is connected by a power supply voltage to the grid 18. charged to a uniform level determined by Once the web reaches the grid potential Then the ions are no longer accelerated between the grid and web surface and have uniform polarity. A charge level is present on the web surface. The second ionizer generates a uniform potential at a high level. Controlling this level will help increase the level. This feature uses a variable output power supply. achieved. This output voltage is connected to an electrostatic voltmeter 34 that measures the voltage on the web. electrically controlled using a feedback loop comprising: to the control circuit 36 This voltage is then compared with the reference voltage and the power supply output voltage is automatically stepped up or down. pressure is applied to maintain a constant voltage level on the web 10.

After the web lO has reached the desired uniform level of electrostatic polar charge, the web is guided Rolls 40, 42, 44, 46 and 48 are followed by grounded applicator rolls. 50, the applicator roll receives emulsion from a suitable source (not shown). A plurality of sliding curtains that generate a free falling curtain 54 that collides on the web A coating hopper 52 is used to coat the web with a liquid coating composition, e.g. A three-layer coating solution of different photographic emulsions is applied. After passing over the coating roll 50, the web 10 is directed to a drying chamber 56 where the emulsion layer is exposed to air or other gas kept at a high temperature. It is dried in contact with the medium, then passed around the guide roll 58 and onto the take-up roll 60. is wound up.

Figure 2 shows a typical method for coating a gelatin silver halide photographic emulsion onto a web surface. - The application speed and static required for uniform application of the ten-coating method. It relates the level of electrical polarity charge. The curve shown in Figure 2 is Fabric conditions (substitute for potash that would cause curve shift under different combinations of application conditions) Typical: Curtain height - 12, acm Curtain flow rate - 1.5 to 6 g/sec per curtain middle mouth Viscosity of coating composition - 60 centipoise Web surface - glossy polyethylene Application point--15'.

Uniform coating is achieved in the left-hand region of the curve in Figure 2, but photo-manufacturing operations Non-uniform coating occurs on the right side of the curve, which would not be useful in this case. paraphrase The curve then represents the dividing line between a satisfactory application and a failed application.

As shown in Figure 2, coating fails at coating speeds up to approximately 250 cm/sec. No polar charge assist is required to prevent . Approximately 250 and approximately 400cm In the region of coating speed between / sec, the curve gradually changes as the polar charge This shows that the need for strikes is increasing. However, usually 250 At speed levels between about 400 cm/sec, satisfactory coating uniformity is achieved. Polar charge assist is not provided as other means may be used to achieve this. curved The slope decreases as the coating speed increases further. The specific coating used Achieves uniform coating over a speed range of 400 to 800 cm/sec. The ratio of charge (measured in volts) to speed (measured in cm/see) It should be noted that the ratio must be at least 1:1. of the present invention Preferred embodiments further include an additional electrostatic charge on the order of 200 volts, e.g. , 600 volts or higher for web speeds of 400 cm/sec. Higher polar charge levels may be required.

Figure 3 shows the flow rate of the coating composition per unit width of the curtain versus the coating speed. Regarding degrees. A uniform application area is shown, but this area is where poor quality application has occurred. is surrounded by a verifiable area. The size and shape of the uniform application area is determined by the curtain. the height of the coating, the viscosity of the coating composition, the coating point, the nature of the web surface and the electrostatic polarity charge. It depends on the level of assist.

In the unstable curtain region, the curtain flow velocity per unit width forms a stable curtain. This is an area where it is too late to move forward. In this area, curtains have many It splits into strands, making it impossible to form a uniform coating. lump (pudding) In the SR region, the curtain speed at the coating point is equal to the web speed. represents a larger state. As a result, the coating composition accumulates behind the curtain and Produces stripes.

For any combination of operating conditions, using electrostatic polar charge assist, e.g. In other words, by applying a sufficiently high level of electrostatic polar charge to the web surface, uniform It is a particularly important feature of the present invention that the application area can be substantially expanded. be. In this way, by using electrostatic polar charge assist, non-uniform coating can be achieved. The coating speed at which this phenomenon begins to occur can be widened. Due to this, Allows certain coating machines to run much faster without making any sacrifices in coating quality. It is possible to operate at higher speeds, thereby producing much more product.

The invention is further illustrated by the following examples.

Goto-Koujisko: Goni G Tsuhi Shiba & E U.S. Patent No. 2.761, except that the hopper was set to apply seven layers at the same time. using a multi-slide bead coating hopper similar to that shown in No. 791. used. The application product is Ektacolor paper (Ekta) containing seven separate layers. ColorPapar). The wet coverage and viscosity of 7N are shown in Table 1. do.

Blue sensitivity (bottom) 32 or 37 6.5 or 4.6 middle layer 5115 Green sensitivity 1550 UV filter 763 Red sensitivity 32 Ultraviolet filter '163 overcoat 793 The viscosity of the bottom layer was adjusted by diluting it with water to obtain sufficient coating properties. Adequate spreadability and Defined as a stable coating system free of mottling, cross lines, microbubbles and other coating defects . Apply this product at high speed (400 cm/sec or more) It was hoped that it would be tried. Table ■ Achieved as a function of bottom layer viscosity and polar charge voltage Indicates the maximum coating speed that can be applied. As shown in Table ■, matte (rough) surface support and a glossy (smooth) surface support were used.

■Beads Co-ingoo 6, 5cps 4.6cps 6.5cps 4.6cps Mat 300cm /sec 350cm/sec 350cm/sec 400cie/sec light Sawa 350cm/sec 400cm/sec 400cm/see ＊＊＊　＊ Polar charge is not required for coating at 400cm/see.

For matte surface supports, as shown in Examples 1(a) and 1(b) Dilution of bottom layer from 6.5 to 4.6 centibore allows maximum application speed of 300 As a result, the speed increases from 350C111/sec to 350C111/sec. The increase was 350 to 400 cm/sec. In Examples I(c) and I(d) As shown, if a polar charge of 350 volts is applied to the support in front of the coating zone, For matte surface supports, the maximum coating speed is 50% for highly dilute bottom layers. cm/sec increased to a maximum of 400 cm/sec. using a matte surface Depending on the viscosity of the bottom layer, the maximum coating speed can be improved by approximately 14% to 17%. Ru. Beads to the extent that polar charges higher than 350 volts can be applied It was found that the coating speed was not improved.

For glossy supports, speeds faster than 400 cm/sec do not provide sufficient coverage. No polar charge was required to achieve fabricability. Glossy supports are generally matte. It is possible to apply at a speed of about 50 cm/sec faster than the front surface. both ties Diluting the bottom layer from 6.5 to 4.6 centipoise gives the best High coating speed increased by 50 cm/sec.

Compared to the known bead coating method, curtain coat is used for applying photographic materials. One advantage of using the dipping method is that the bottom layer does not need to be diluted any further than the other layers. It is well known that this is the case. High dilution bottom layer in bead coating This is in contrast to the need to use . At the top, a total of 40% of the water is at the bottom. It's in the layer. The speed at which a continuously coated web support can be dried due to this requirement tends to be limited. The bottom layer in the bead coating method is usually 10 cm. Stable free fall of less than a chipoise, preferably 3-5 centipoise The outer layer of the curtain is typically 40 centipoise or higher. Apply high viscosity coating composition The advantages of fabrics are well known and described by Hughes, U.S. Pat. No. 3+ No. 508-947, continuous and uniformly delicate photographic coating The water addition requirements on the dryer where the material must be dried can be significantly reduced. This is one advantage.

1-Curtain coating method The hopper is set so that seven layers of the coating composition can be applied at the same time. No. 3,508,947, a multiple sliding curtain cord similar to that shown in Figure 1 of No. 3,508,947. using a ting hopper. Viscosity and wetting of all layers except the bottom (blue-sensitive) layer The coverage was the same as shown in Table 1. bottom (blue sensitivity) ) layer with a coating composition having a wet coverage of 20 microns and a viscosity of 26 centipoise and a removal allowance. I got it. Table 1 shows the coating speeds obtained using the matte support side and the glossy support side. to be displayed.

■　Kaan Kho Gugo Bottom layer viscosity 26 centipoise, wet coverage 20 micron matte 400 cm/se c Unnecessary **Polar charge is not required for coating at 400Ω/sec.

From the data recorded in Table ■, 400 cm/s for bead coating. Requires use of 350 volts polar charge to apply at maximum speed of ec However, the curtain coating method does not require polar charge assist. It will be shown that such speeds could be achieved.

However, the application requirements for glossy supports have been found to be quite different. and therefore cannot be predicted based on conventional knowledge of bead coating methods. Met. For example, Table 1 shows that if polar charge assist is not used, 26 With a Chipoise bottom layer, only 300 am/sec for glossy supports It shows that only the maximum application speed is achieved. bead coating Table 2 on the Glossy Surface shows that the 400C This shows that a maximum coating speed of m/sec was achieved.

Shiny surface support when a 700 volt polar charge is applied to the coating surface in front of the coating point. The body can be curtain coated at a speed of at least 500cm/see. Ta. This results in a glossy support surface compared to that obtained without polar charges. The achievable curtain coating speed has increased by at least 67% for It turns out. As shown in Figure 2, using progressively higher levels of polar charge, In this case, it is possible to apply with higher speed.

From these examples, using a bead coating method that requires a highly diluted (low viscosity) bottom layer Coating photographic materials has an upper limit of coating speed of approximately 400 cm/sec. will be shown.

When applying photographic materials using the curtain coating method with polar charge assist. Unexpectedly, it has been found that even faster application speeds are possible when did. When curtain coating is used, a highly concentrated (high viscosity) bottom layer is applied. Also, extremely high levels of By applying a polar charge, coating speeds of well over 400 em/sec can be obtained. It turned out to be something unexpected.

The scope of the claims 1. Advance the object along a path through the coating zone and apply one or more layers of liquid. a free-falling curtain comprising a body-applied composition and extending across the path; A coating consisting of one or more layers is applied to the moving object by impinging it on the moving object in the fabric zone. In a method of applying a liquid coating composition to an object, the method comprises: The above-mentioned step in which the coating material is applied while moving the material forward at a speed of 250 cm+/sec. Applying an electrostatic polar charge on the surface of an object, at any point on said surface, in volts The ratio of the measured charge to the speed measured in cm/sec is small. Select the amount of charge according to the speed of the object so that at least l:1. An improvement method comprising:

2. Applying an electrostatic polarity charge that is 200 volts greater than the voltage obtained from the above ratio. A further improvement method according to claim 1, comprising:

3. The object advancing along the path through the application zone is a web and the free-falling force For the manufacture of photographic elements in which the liquid coating composition forming the coating is a liquid photographic coating composition. and the web advances at a speed of at least 400 cm/sec. A further improvement method according to claim 1 or 2 comprising:

4. A width narrower than the width of the web so that the web overhangs the coating roll. The coating roll passes around the applicator roll, and the area extending from the applicator roller A greater amount of electrostatic polar charge is placed on the web surface than on the rest of the web surface. 4. A further improvement method according to claim 3, comprising applying the voltage onto a web.

5. Claim 3, wherein the web is made of cellulose acetate film, or Method of Section 4.

6. Claim 3 or 3, wherein the web is made of polyethylene terephthalate. Method in Section 4.

7. The person according to claim 3 or 4, wherein the web is made of polyethylene-coated paper. Law.

8. A claim in which at least one of the layers comprises a gelatin silver halide photographic emulsion. The method of paragraph 3 or paragraph 4.

9. Move the object to be coated along the path at least 250 cm through the coating zone. means for advancing at a speed of /sec; one or more layers extending across said path; forming a free-falling curtain of a layer of liquid coating composition within said coating zone; The moving object is made to collide with the surface of the moving object, and a coating material consisting of one or more layers is applied thereon. means for forming an electrostatic polar charge on the surface of said object to which said coating is applied; is applied, the amount of which comprises am/sec of said charge measured in volts. -Ten coating equipment.

10. said object is a web and said means for advancing said object is controlled and predetermined; The billing system is a web conveying system that can be operated at a defined speed. Curtain coating equipment of scope item 9.

11. The electrostatic charge is a bond charge or a polar charge, and before applying the electrostatic polar charge Packing roll with earthed recording means and at least one grid-control ion 10. The curtain coating apparatus according to claim 9, comprising a coating apparatus.

12. The means for forming a free-falling curtain comprises a plurality of slide hoppers. The curtain coating apparatus according to claim 9.

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Claims (17)

[Claims] 1. The object is advanced along a path through the coating zone and coated with one or more layers of liquid. a free-falling curtain comprising a body-applied composition and extending across the path; A coating consisting of one or more layers is applied to the moving object by impinging it on the moving object in the fabric zone. In the method of applying a liquid coating composition to an object, the composition is applied to an object. Apply an electrostatic polar charge on the surface of the object to be coated, and adjust the amount of the charge to the surface of the object to be coated. The method of improvement comprises: 2. The object is advanced along a path through the coating zone and coated with one or more layers of liquid. a free-falling curtain comprising a body-applied composition and extending across the path; A coating consisting of one or more layers is applied to the moving object by impinging it on the moving object in the fabric zone. In a method of applying a liquid coating composition to an object, the method comprises: The above-mentioned object is moved forward at a speed of 250 cm/sec and applies the above-mentioned coating material. Apply an electrostatic polar charge on the surface of a body and measure it in volts at any point on said surface. the ratio of the determined charge to the speed measured in cm/sec is small; The amount of charge is selected according to the speed of the object so that the ratio is 1:1. An improvement method that includes: 3. Advance the web along the path through the application zone and apply a single layer of liquid photo applying a free-falling curtain comprising a coating composition and extending across the path; fabrication of a photographic element impinging on said web in a zone to form a coating thereon; In the manufacturing method, an even coating of the coating material is applied onto the surface of the web to which the coating material is applied. An improvement comprising applying an electrostatic polar charge in an amount sufficient to enhance uniformity. Law. 4. Advance the web along the path through the application zone and apply a single layer of liquid photo applying a free-falling curtain comprising a coating composition and extending across the path; Manufacturing a photographic element impinging on said web in a zone to form a coating thereon. In the method, the web is advanced at a speed of at least 400 cm/sec. and applying an electrostatic polar charge on the surface of the web to which the coating material is applied; of said charge, measured in volts, at any point on the surface, measured in cm/sec. The speed of the web is such that the ratio to the speed of the web is at least 1:1. An improved method comprising selecting the amount of charge according to. 5. Advancing the web along a path through the application zone and applying multiple layers of liquid applying a free-falling curtain comprising a coating composition and extending across the path; of a photographic element impinged upon said web within a zone to form a multilayer coating thereon; In the manufacturing method, the multilayer coating is performed on the surface of the web to which the coating material is applied. comprising applying an electrostatic polar charge in an amount sufficient to increase the uniformity of the object. Improvement method. 6. A width narrower than the width of the web is also provided so that the web overhangs the application roll. The web passes around a coating roll and a static electricity is applied onto the web. Electrical polar charges remain on the web surface in areas extending from the applicator roll. 6. The method of claim 5, wherein the method of claim 5 is of a greater amount than on said web surface. 7. Advancing the web along a path through the application zone and applying multiple layers of liquid applying a free-falling curtain comprising a coating composition and extending across the path; of a photographic element impinged upon said web within a zone to form a multilayer coating thereon; In the manufacturing method, the web is advanced at a speed of at least 400 cm/sec. applying an electrostatic polar charge on the surface of the web to which the multilayer coating is applied; and the charge, measured in volts, at any point on the surface, in cm/sec The speed of the web is such that the ratio to the measured speed is at least 1:1. An improved method of selecting the amount of charge according to speed. 8. The method according to claim 7, wherein the web is made of cellulose acetate film. Law. 9. 8. The method of claim 7, wherein said web comprises polyethylene terephthalate. . 10. 8. The method of claim 7, wherein said web is polyethylene coated paper. 11. Claims wherein at least one of said layers comprises a gelatin silver halide photographic emulsion. The method in Box 7. 12. the amount of charge measured in volts is at least 8. The method of claim 7, wherein the speed of the web is equal to the speed of the web plus 100. 13. means for advancing the object to be coated along a path through the coating zone; a free-falling channel of one or more layers of liquid coating composition extending across said path; 1. forming a coating film and impinging it on the surface of the moving object within the application zone; means for forming thereon a coating comprising a layer or layers; and applying said coating. an electrostatic electrode on the surface of said object in an amount sufficient to increase the uniformity of said application. Means of applying a sexual charge Curtain coating equipment comprising: 14. The advancing means advances the object at a speed of at least 250 cm/sec. and the charge applying means is capable of causing the charge, measured in volts, to to said speed measured in cm/sec is at least 1:1. It is possible to apply an amount of electrostatic polar charge such that -Ten coating equipment. 15. said object is a web and said means for advancing said object is controlled and predetermined; The billing system is a web conveying system that can be operated at a defined speed. Curtain coating equipment according to scope item 14. 16. If the electrostatic charge is a bond charge or a polar charge, before applying the electrostatic polar charge A backing roll with a grounded recording means and at least one grid control iodine. 15. The curtain coating apparatus of claim 14, comprising a coating apparatus. 17. The means for forming a free-falling curtain comprises a plurality of sliding hoppers. The curtain coating apparatus according to claim 14.